The present disclosure relates to laterally diffused metal oxide semiconductor (LDMOS) devices and methods of making the same.
A depletion type MOSFET (DMOSFET) based on planar diffusion technology is one of the semiconductor devices used in the fields of switching mode power supply devices, lamp stabilization circuits and motor drive circuits, and in particular, laterally diffused metal oxide semiconductor (LDMOS) transistors have been developed.
A lateral double diffused metal oxide semiconductor (LDMOS) device is a typical example of a horizontal power device that provides rapid switching response and high input impedance by means of a majority carrier device. FIG. 1 is a graph illustrating the breakdown voltage characteristics of an LDMOS device in the case where the doping concentration of a P-type well decreases due to the device isolation layer structure.
In order to operate as a high-voltage device, the LDMOS device must maintain a high breakdown voltage and a low on-resistance (Ron). However, a P-type body is designed to have a sufficiently high doping concentration to prevent punch-through breakdown when applying a reverse bias voltage against a high voltage. However, the doping concentration of a P-type well typically decreases during a high-temperature thermal treatment process in the process of forming a device isolation region that isolates the P-type body and the P-type well.
Thus, a leakage current is generated due to depletion of dopant in the P-type well during thermal treatment, and it is difficult to achieve a targeted breakdown voltage, as illustrated in the graph of FIG. 2.
What is therefore desired is a technology for providing an LDMOS device that has a high breakdown voltage and good I-V characteristics by maintaining a fixed dopant concentration in a P-type well.